This kind of centrifugal separator is intended for cleaning of gases, such as air, especially contaminated or heavily contaminated air. Thereby it can in particular concern air in industrial environments, for instance air immediately in the proximity of various kinds of machines. Furthermore, this kind of centrifugal separators may be intended to be used for cleaning of other gases. For instance exhaust gases from stationary or mobile combustion engines.
One problem in connection with such cleaning is that the impurities which are contained in the gas to be cleaned contain a large proportion of solid or liquid particles which are very small and/or which have a relatively low density. Such small particles are difficult to separate also by means of centrifugal separators. A further problem in connection with such cleaning is that the particulate impurities contained in the gas to be cleaned get caught in the rotating member, and especially to the separation discs which frequently are provided on the rotating member for rendering the separation efficient. Impurities, which may consist of both liquid and particulate impurities, form a more or less solid coating on the rotating member. This coating deteriorates the separation and makes it difficult to transport the impurities out from the separation space. Dry, i.e. solid, particles have a tendency to get caught on these surfaces, and thus form a relatively solid coating on the surfaces of the rotating member and in the separation space.